The instant disclosure relates to electrophysiological mapping, such as may be performed in cardiac diagnostic and therapeutic procedures. In particular, the instant disclosure relates to systems, apparatuses, and methods for mapping cardiac restitution.
“Restitution” refers to a functional relationship between the duration of a cardiac action potential and the length of the quiescent interval preceding it. In many cases, this relationship reflects limited change in action potential duration (“APD”) over a broad range of long diastolic intervals (“DI”) and shortening of the APD at shorter DIs. APD restitution can therefore be thought of as a form of adaptation to changes in heart rate.
An APD restitution curve can be constructed by varying the DI and plotting the resulting APD. To the first order, an APD restitution curve reflects the underlying dynamics of the system during steady-state conditions. For APD restitution curves with steep slopes (i.e., greater than one), small changes in DI result in large changes in APD. On the other hand, for APD restitution curves with shallow slopes (i.e., less than one), small changes in DI are damped out over subsequent beats. Research has shown that steep restitution slopes can lead to breakup of spiral waves in tissue.
“Cardiac electrogram restitution” is an analogous functional relationship between the length of a preceding interval (e.g., cycle length or DI) and the successive duration (e.g., APD, activation recovery interval (“ARI”), or EGM width). This relationship shows a form of adaptation to changes in heart rate and studies tissue properties that control the dynamic behavior of the heart.
It would be desirable to map cardiac restitution in real time during an electrophysiology (“EP”) study.